It's easy to see how Jeremiah's name became a byword for pessimism. The Prophet Hananiah had prophesied that everything would turn out for the best; the exiles and the booty taken away to Babylon would be returned. It was the message that everyone wanted to hear, but Jeremiah would have none of it.
In his opinion a true prophet is like Private Fraser from the old TV sitcom "Dad's Army". He - or she - only speaks words of doom about war, famine, and pestilence. If a prophet speaks words of peace we should be on our guard and believe them only then those words come true.
We might feel that Jeremiah is exaggerating a bit. He leaves no room for prophets who speak words of inspiration and encouragement, who dream of a better world or of new possibilities. Martin Luther King was this kind of prophet, and there were prophets like this in the Isaiah tradition.
As someone said recently on Radio 4's "Start The Week" programme, pessimists like Jeremiah are never disappointed. If things turn out as badly as they expected, then they get to say, 'We told you so!' If things turn out better than expected, they are pleasantly surprised!
But I'm sure this wasn't the motivation for Jeremiah's harsh view of prophecy. To his mind prophecy is really about judgement, about warning people when they are taking unnecessary and foolish risks or behaving in an immoral way. To this way of thinking, you don't need a prophet to announce good news.
This is why it's always dangerous when Christian commentators tells us not to worry too much about global warming or injustice. It's true that the Christian message is supposed to be good news for humankind, but that doesn't mean Christians can safely become carefree optimists. We have a duty of care for the earth and our neighbours which means that we are always under judgement when things start to go wrong. Those who too quickly tell us that we need not worry after all, and everything is putting itself to rights, are just as dangerous as the little boy who cried "Wolf!" They can lull us into a sense of false security.
Paul reminds us here that we can never plead human frailty as an excuse for doing things which we know are actually wrong and contrary to God's will. Because we have the free gift of God's grace working in us, we do receive pardon for the wrong things we do, but we are also expected to strive to meet God's standards of behaviour. The more time we spend thinking about God's goodness, identifying ourselves with God's will and seeking to be in relationship with God's Spirit, the harder it will become to do wrong. In fact, we should allow ourselves to become just as much enslaved to God's nature as we were once enslaved to human nature. It may never happen, but that should always be our aim!
Are these gnomic sayings telling disciples that practical deeds of goodness, and a readiness to identify ourselves with the truth - wherever it comes from - is more important than party allegiances or the labels we attach to one another?